// This code is derived from jcifs smb client library <jcifs at samba dot org>
// Ported by J. Arturo <webmaster at komodosoft dot net>
//  
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
// 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
// 
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
using System.IO;
using SharpCifs.Util.Sharpen;

namespace SharpCifs.Netbios
{
    public abstract class SessionServicePacket
    {
        internal const int SessionMessage = unchecked(0x00);

        internal const int SessionRequest = unchecked(0x81);

        public const int PositiveSessionResponse = unchecked(0x82);

        public const int NegativeSessionResponse = unchecked(0x83);

        internal const int SessionRetargetResponse = unchecked(0x84);

        internal const int SessionKeepAlive = unchecked(0x85);

        internal const int MaxMessageSize = unchecked(0x0001FFFF);

        internal const int HeaderLength = 4;

        // session service packet types 
        internal static void WriteInt2(int val, byte[] dst, int dstIndex)
        {
            dst[dstIndex++] = unchecked((byte)((val >> 8) & unchecked(0xFF)));
            dst[dstIndex] = unchecked((byte)(val & unchecked(0xFF)));
        }

        internal static void WriteInt4(int val, byte[] dst, int dstIndex)
        {
            dst[dstIndex++] = unchecked((byte)((val >> 24) & unchecked(0xFF)));
            dst[dstIndex++] = unchecked((byte)((val >> 16) & unchecked(0xFF)));
            dst[dstIndex++] = unchecked((byte)((val >> 8) & unchecked(0xFF)));
            dst[dstIndex] = unchecked((byte)(val & unchecked(0xFF)));
        }

        internal static int ReadInt2(byte[] src, int srcIndex)
        {
            return ((src[srcIndex] & unchecked(0xFF)) << 8)
                    + (src[srcIndex + 1] & unchecked(0xFF));
        }

        internal static int ReadInt4(byte[] src, int srcIndex)
        {
            return ((src[srcIndex] & unchecked(0xFF)) << 24)
                    + ((src[srcIndex + 1] & unchecked(0xFF)) << 16)
                    + ((src[srcIndex + 2] & unchecked(0xFF)) << 8)
                    + (src[srcIndex + 3] & unchecked(0xFF));
        }

        internal static int ReadLength(byte[] src, int srcIndex)
        {
            srcIndex++;
            return ((src[srcIndex++] & unchecked(0x01)) << 16)
                    + ((src[srcIndex++] & unchecked(0xFF)) << 8)
                    + (src[srcIndex++] & unchecked(0xFF));
        }

        /// <exception cref="System.IO.IOException"></exception>
        internal static int Readn(InputStream @in, byte[] b, int off, int len)
        {
            int i = 0;
            int n;
            while (i < len)
            {
                n = @in.Read(b, off + i, len - i);
                if (n <= 0)
                {
                    break;
                }
                i += n;
            }
            return i;
        }

        /// <exception cref="System.IO.IOException"></exception>
        internal static int ReadPacketType(InputStream @in, byte[] buffer, int bufferIndex)
        {
            int n;
            if ((n = Readn(@in, buffer, bufferIndex, HeaderLength)) != HeaderLength)
            {
                if (n == -1)
                {
                    return -1;
                }
                throw new IOException("unexpected EOF reading netbios session header");
            }
            int t = buffer[bufferIndex] & unchecked(0xFF);
            return t;
        }

        internal int Type;

        internal int Length;

        public virtual int WriteWireFormat(byte[] dst, int dstIndex)
        {
            Length = WriteTrailerWireFormat(dst, dstIndex + HeaderLength);
            WriteHeaderWireFormat(dst, dstIndex);
            return HeaderLength + Length;
        }

        /// <exception cref="System.IO.IOException"></exception>
        internal virtual int ReadWireFormat(InputStream @in, byte[] buffer, int bufferIndex)
        {
            ReadHeaderWireFormat(@in, buffer, bufferIndex);
            return HeaderLength + ReadTrailerWireFormat(@in, buffer, bufferIndex);
        }

        internal virtual int WriteHeaderWireFormat(byte[] dst, int dstIndex)
        {
            dst[dstIndex++] = unchecked((byte)Type);
            if (Length > unchecked(0x0000FFFF))
            {
                dst[dstIndex] = unchecked(unchecked(0x01));
            }
            dstIndex++;
            WriteInt2(Length, dst, dstIndex);
            return HeaderLength;
        }

        /// <exception cref="System.IO.IOException"></exception>
        internal virtual int ReadHeaderWireFormat(InputStream @in, byte[] buffer, int bufferIndex)
        {
            Type = buffer[bufferIndex++] & unchecked(0xFF);
            Length = ((buffer[bufferIndex] & unchecked(0x01)) << 16)
                        + ReadInt2(buffer, bufferIndex + 1);
            return HeaderLength;
        }

        internal abstract int WriteTrailerWireFormat(byte[] dst, int dstIndex);

        /// <exception cref="System.IO.IOException"></exception>
        internal abstract int ReadTrailerWireFormat(InputStream @in, byte[] buffer, int bufferIndex);
    }
}
